Polyunsaturated linoleic acids with conjugated double bonds, which are commercially available as “CLA” (conjugated linoleic acids), belong to the essential fatty acids for human beings and animals and are therefore used as food additives. Conjugated linoleic acid is normally produced from triglycerides which have a high percentage content of—normally unconjugated—linoleic acid, such as thistle or sunflower oil for example. The triglycerides are isomerized in the presence of basic catalysts and then saponified. A disadvantage in this regard is that, on the one hand, the saponification step yields many unwanted waste materials and, on the other hand, large quantities of alkalis are required, which can quickly result in corrosion in the reactors used. To avoid this, linoleic acid alkyl esters have more recently been used as preferred starting materials and, in a first step, are isomerized to the CLA esters and then saponified. In this process, however, utilization of reactor capacity is often very poor. The profitability of the process is seriously restricted by large volumes of water, poor yields and unwanted secondary products.
Accordingly, the problem addressed by the present invention was to provide a process for the production of conjugated linoleic acid which would be distinguished by very high profitability and which would lead to an end product in high yields and purity.